How can people know God exists without the Bible?
God has made the knowledge of Himself manifest within people and clearly seen in creation. His invisible attributes, eternal power, and Godhead are understood through the things that are made, leaving the whole human race without excuse, according to Romans 1.
Les teaches from Romans 1:18-20 that God's wrath is revealed from heaven against all ungodliness and unrighteousness of men who hold the truth in unrighteousness. Yet that which may be known of God is manifest in them, for God has already shown it to them. Les explains that 'manifest' is a multi-type term, like a manifold on a V8 engine with eight portholes, signifying a complete unveiling of knowledge. The invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even His eternal power and Godhead, so that they—the whole human race—are without excuse. Les adds that this does not mean we can just sit in our living room and let the world go to hell; we are to promote the gospel to the ends of the earth.
For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: